With a gasoline engine causing a mixture of fuel and air that was mixed in advance to combust by the ignition spark from a spark plug, knocking has been known to occur by the uncombusted mixture (end gas) isolated from the spark plug auto igniting. Knocking tends to occur when raising the compression ratios of engines; therefore, with the high-compression engines of recent years, the suppression of knocking has been strongly demanded.
A method which retards the ignition timing has been given as a method for suppressing knocking. However, when retarding the ignition timing, the fuel efficiency of the engine declines. For this reason, the development of technology whereby high fuel efficiency is obtained while suppressing knocking is demanded also for high-compression engines.
However, since knocking can be suppressed by raising the octane rating of fuel, alcohol-containing fuel produced by mixing alcohols such as ethanol into gasoline in advance has been widely used as fuel with high octane rating in some regions. In addition, accompanying the spread of such alcohol-containing fuels, the development of technology for separating the alcohol-containing fuels refueled from outside into fuel of high gasoline concentration and fuel of high alcohol concentration onboard the vehicle is being advanced. This is because, since there are various points of difference in the fuel properties such as octane rating and heating value between gasoline and alcohol, for example, it is more preferable to separate onboard the vehicle and use gasoline and alcohol differently depending on the application, than using alcohol-containing fuel that was filled from outside as is. However, separation that depends on the demand of the engine is not easy.
On the other hand, a synthesis method has been proposed that causes hydrocarbons to convert to alcohols using a carbon-radical generating catalyst such as N-hydroxyphthalimide (NHPI) (refer to Non-Patent Document 1, for example). If it were possible to use this synthesis method onboard the vehicle, it is considered to be possible to convert hydrocarbons contained in gasoline into alcohols of high octane rating according to the demand of the engine, and possible to supply the alcohols of high octane rating to the engine.
Non-Patent Document 1: S. Sakaguchi, S. Kato, T. Iwahama, Y. Ishii; Bull. Chem. Soc. Jpn., 71 (1998) pp. 1237-1240